我正在尝试在我的代码中实现Data transformation using Reflection 1 示例。
GetSourceValue函数有一个比较各种类型的开关，但是我想删除这些类型和属性，并且GetSourceValue只使用一个字符串作为参数来获取属性的值。我想在字符串中传递一个类和属性并解析属性的值。
这可能吗？
答案 0 :(得分：1548)
public static object GetPropValue(object src, string propName)
{
return src.GetType().GetProperty(propName).GetValue(src, null);
}
当然，你会想要添加验证和诸如此类的东西，但这就是它的要点。
答案 1 :(得分：191)
这样的事情怎么样：
public static Object GetPropValue(this Object obj, String name) {
foreach (String part in name.Split('.')) {
if (obj == null) { return null; }
Type type = obj.GetType();
PropertyInfo info = type.GetProperty(part);
if (info == null) { return null; }
obj = info.GetValue(obj, null);
}
return obj;
}
public static T GetPropValue<T>(this Object obj, String name) {
Object retval = GetPropValue(obj, name);
if (retval == null) { return default(T); }
// throws InvalidCastException if types are incompatible
return (T) retval;
}
这将允许您使用单个字符串进入属性，如下所示：
DateTime now = DateTime.Now;
int min = GetPropValue<int>(now, "TimeOfDay.Minutes");
int hrs = now.GetPropValue<int>("TimeOfDay.Hours");
您可以将这些方法用作静态方法或扩展。
答案 2 :(得分：54)
添加到任何Class：
public class Foo
{
public object this[string propertyName]
{
get { return this.GetType().GetProperty(propertyName).GetValue(this, null); }
set { this.GetType().GetProperty(propertyName).SetValue(this, value, null); }
}
public string Bar { get; set; }
}
然后，您可以使用as：
Foo f = new Foo();
// Set
f["Bar"] = "asdf";
// Get
string s = (string)f["Bar"];
答案 3 :(得分：42)
使用Microsoft.VisualBasic命名空间CallByName（Microsoft.VisualBasic.dll）怎么样？它使用反射来获取普通对象，COM对象甚至动态对象的属性，字段和方法。
using Microsoft.VisualBasic;
using Microsoft.VisualBasic.CompilerServices;
然后
Versioned.CallByName(this, "method/function/prop name", CallType.Get).ToString();
答案 4 :(得分：26)
jheddings给出了很好的答案。我想改进它，允许引用聚合数组或对象集合，以便propertyName可以是property1.property2 [X] .property3：
public static object GetPropertyValue(object srcobj, string propertyName)
{
if (srcobj == null)
return null;
object obj = srcobj;
// Split property name to parts (propertyName could be hierarchical, like obj.subobj.subobj.property
string[] propertyNameParts = propertyName.Split('.');
foreach (string propertyNamePart in propertyNameParts)
{
if (obj == null) return null;
// propertyNamePart could contain reference to specific
// element (by index) inside a collection
if (!propertyNamePart.Contains("["))
{
PropertyInfo pi = obj.GetType().GetProperty(propertyNamePart);
if (pi == null) return null;
obj = pi.GetValue(obj, null);
}
else
{ // propertyNamePart is areference to specific element
// (by index) inside a collection
// like AggregatedCollection[123]
// get collection name and element index
int indexStart = propertyNamePart.IndexOf("[")+1;
string collectionPropertyName = propertyNamePart.Substring(0, indexStart-1);
int collectionElementIndex = Int32.Parse(propertyNamePart.Substring(indexStart, propertyNamePart.Length-indexStart-1));
// get collection object
PropertyInfo pi = obj.GetType().GetProperty(collectionPropertyName);
if (pi == null) return null;
object unknownCollection = pi.GetValue(obj, null);
// try to process the collection as array
if (unknownCollection.GetType().IsArray)
{
object[] collectionAsArray = unknownCollection as object[];
obj = collectionAsArray[collectionElementIndex];
}
else
{
// try to process the collection as IList
System.Collections.IList collectionAsList = unknownCollection as System.Collections.IList;
if (collectionAsList != null)
{
obj = collectionAsList[collectionElementIndex];
}
else
{
// ??? Unsupported collection type
}
}
}
}
return obj;
}
答案 5 :(得分：12)
如果我使用Ed S.中的代码，我会
由于其保护级别，'ReflectionExtensions.GetProperty（Type，string）'无法访问
似乎GetProperty()在Xamarin.Forms中不可用。我的可移植类库（.NET Framework 4.5，Windows 8，ASP.NET Core 1.0，Xamarin.Android，Xamarin.iOS，Xamarin.iOS Classic）中TargetFrameworkProfile为Profile7。
现在我找到了一个有效的解决方案：
using System.Linq;
using System.Reflection;
public static object GetPropValue(object source, string propertyName)
{
var property = source.GetType().GetRuntimeProperties().FirstOrDefault(p => string.Equals(p.Name, propertyName, StringComparison.OrdinalIgnoreCase));
return property?.GetValue(source);
}
答案 6 :(得分：10)
关于嵌套属性讨论，如果您使用DataBinder.Eval Method (Object, String)，可以避免所有反射内容：
var value = DataBinder.Eval(DateTime.Now, "TimeOfDay.Hours");
当然，您需要添加对System.Web程序集的引用，但这可能不是什么大问题。
答案 7 :(得分：6)
.NET Standard中的调用方法发生了变化（截至1.6）。我们也可以使用C＃6的空条件运算符。
using System.Reflection;
public static object GetPropValue(object src, string propName)
{
return src.GetType().GetRuntimeProperty(propName)?.GetValue(src);
}
答案 8 :(得分：4)
使用 System.Reflection 命名空间的PropertyInfo。无论我们尝试访问什么属性，反射编译都很好。错误将在运行时出现。
public static object GetObjProperty(object obj, string property)
{
Type t = obj.GetType();
PropertyInfo p = t.GetProperty("Location");
Point location = (Point)p.GetValue(obj, null);
return location;
}
它可以正常获取对象的Location属性
Label1.Text = GetObjProperty(button1, "Location").ToString();
我们将获得位置：{X = 71，Y = 27} 我们也可以以同样的方式返回location.X或location.Y。
答案 9 :(得分：4)
public static List<KeyValuePair<string, string>> GetProperties(object item) //where T : class
{
var result = new List<KeyValuePair<string, string>>();
if (item != null)
{
var type = item.GetType();
var properties = type.GetProperties(BindingFlags.Public | BindingFlags.Instance);
foreach (var pi in properties)
{
var selfValue = type.GetProperty(pi.Name).GetValue(item, null);
if (selfValue != null)
{
result.Add(new KeyValuePair<string, string>(pi.Name, selfValue.ToString()));
}
else
{
result.Add(new KeyValuePair<string, string>(pi.Name, null));
}
}
}
return result;
}
这是一种在List中获取所有属性及其值的方法。
答案 10 :(得分：3)
public static TValue GetFieldValue<TValue>(this object instance, string name)
{
var type = instance.GetType();
var field = type.GetFields(BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance).FirstOrDefault(e => typeof(TValue).IsAssignableFrom(e.FieldType) && e.Name == name);
return (TValue)field?.GetValue(instance);
}
public static TValue GetPropertyValue<TValue>(this object instance, string name)
{
var type = instance.GetType();
var field = type.GetProperties(BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance).FirstOrDefault(e => typeof(TValue).IsAssignableFrom(e.PropertyType) && e.Name == name);
return (TValue)field?.GetValue(instance);
}
答案 11 :(得分：3)
public class YourClass
{
//Add below line in your class
public object this[string propertyName] => GetType().GetProperty(propertyName)?.GetValue(this, null);
public string SampleProperty { get; set; }
}
//And you can get value of any property like this.
var value = YourClass["SampleProperty"];
答案 12 :(得分：2)
这是另一种查找嵌套属性的方法，该属性不需要字符串告诉您嵌套路径。感谢Ed S.的单一属性方法。
public static T FindNestedPropertyValue<T, N>(N model, string propName) {
T retVal = default(T);
bool found = false;
PropertyInfo[] properties = typeof(N).GetProperties();
foreach (PropertyInfo property in properties) {
var currentProperty = property.GetValue(model, null);
if (!found) {
try {
retVal = GetPropValue<T>(currentProperty, propName);
found = true;
} catch { }
}
}
if (!found) {
throw new Exception("Unable to find property: " + propName);
}
return retVal;
}
public static T GetPropValue<T>(object srcObject, string propName) {
return (T)srcObject.GetType().GetProperty(propName).GetValue(srcObject, null);
}
答案 13 :(得分：2)
以下代码是一种递归方法，用于显示对象实例中包含的所有属性名称和值的整个层次结构。此方法在此主题中使用上面AlexD的GetPropertyValue()答案的简化版本。感谢这个讨论主题，我能够弄清楚如何做到这一点！
例如，我使用此方法通过调用方法显示WebService响应中所有属性的爆炸或转储：
PropertyValues_byRecursion("Response", response, false);
public static object GetPropertyValue(object srcObj, string propertyName)
{
if (srcObj == null)
{
return null;
}
PropertyInfo pi = srcObj.GetType().GetProperty(propertyName.Replace("[]", ""));
if (pi == null)
{
return null;
}
return pi.GetValue(srcObj);
}
public static void PropertyValues_byRecursion(string parentPath, object parentObj, bool showNullValues)
{
/// Processes all of the objects contained in the parent object.
/// If an object has a Property Value, then the value is written to the Console
/// Else if the object is a container, then this method is called recursively
/// using the current path and current object as parameters
// Note: If you do not want to see null values, set showNullValues = false
foreach (PropertyInfo pi in parentObj.GetType().GetTypeInfo().GetProperties())
{
// Build the current object property's namespace path.
// Recursion extends this to be the property's full namespace path.
string currentPath = parentPath + "." + pi.Name;
// Get the selected property's value as an object
object myPropertyValue = GetPropertyValue(parentObj, pi.Name);
if (myPropertyValue == null)
{
// Instance of Property does not exist
if (showNullValues)
{
Console.WriteLine(currentPath + " = null");
// Note: If you are replacing these Console.Write... methods callback methods,
// consider passing DBNull.Value instead of null in any method object parameters.
}
}
else if (myPropertyValue.GetType().IsArray)
{
// myPropertyValue is an object instance of an Array of business objects.
// Initialize an array index variable so we can show NamespacePath[idx] in the results.
int idx = 0;
foreach (object business in (Array)myPropertyValue)
{
if (business == null)
{
// Instance of Property does not exist
// Not sure if this is possible in this context.
if (showNullValues)
{
Console.WriteLine(currentPath + "[" + idx.ToString() + "]" + " = null");
}
}
else if (business.GetType().IsArray)
{
// myPropertyValue[idx] is another Array!
// Let recursion process it.
PropertyValues_byRecursion(currentPath + "[" + idx.ToString() + "]", business, showNullValues);
}
else if (business.GetType().IsSealed)
{
// Display the Full Property Path and its Value
Console.WriteLine(currentPath + "[" + idx.ToString() + "] = " + business.ToString());
}
else
{
// Unsealed Type Properties can contain child objects.
// Recurse into my property value object to process its properties and child objects.
PropertyValues_byRecursion(currentPath + "[" + idx.ToString() + "]", business, showNullValues);
}
idx++;
}
}
else if (myPropertyValue.GetType().IsSealed)
{
// myPropertyValue is a simple value
Console.WriteLine(currentPath + " = " + myPropertyValue.ToString());
}
else
{
// Unsealed Type Properties can contain child objects.
// Recurse into my property value object to process its properties and child objects.
PropertyValues_byRecursion(currentPath, myPropertyValue, showNullValues);
}
}
}
答案 14 :(得分：2)
你永远不会提到你正在检查的对象，因为你拒绝那些引用给定对象的对象，我会认为你的意思是静态的。
using System.Reflection;
public object GetPropValue(string prop)
{
int splitPoint = prop.LastIndexOf('.');
Type type = Assembly.GetEntryAssembly().GetType(prop.Substring(0, splitPoint));
object obj = null;
return type.GetProperty(prop.Substring(splitPoint + 1)).GetValue(obj, null);
}
请注意，我使用局部变量obj标记了正在检查的对象。 null表示静态，否则将其设置为您想要的。另请注意，GetEntryAssembly()是获得“运行”程序集的几种可用方法之一，如果您在加载类型时遇到困难，可能需要使用它。
答案 15 :(得分：1)
更短的方式......
var a = new Test { Id = 1 , Name = "A" , date = DateTime.Now};
var b = new Test { Id = 1 , Name = "AXXX", date = DateTime.Now };
var compare = string.Join("",a.GetType().GetProperties().Select(x => x.GetValue(a)).ToArray())==
string.Join("",b.GetType().GetProperties().Select(x => x.GetValue(b)).ToArray());
答案 16 :(得分：1)
Dim NewHandle As YourType = CType(Microsoft.VisualBasic.CallByName(ObjectThatContainsYourVariable, "YourVariableName", CallType), YourType)
答案 17 :(得分：1)
jheddings和AlexD都就如何解析属性字符串写了很好的答案。我想把它扔进去，因为我为此目的写了一个专门的库。
Pather.CSharp的主要课程是Resolver。默认情况下，它可以解析属性，数组和字典条目。
所以，例如，如果你有一个像这样的对象
var o = new { Property1 = new { Property2 = "value" } };
想要获得Property2，你可以这样做：
IResolver resolver = new Resolver();
var path = "Property1.Property2";
object result = r.Resolve(o, path);
//=> "value"
这是它可以解决的路径的最基本的例子。如果您想了解它还能做什么，或者如何扩展它，只需前往Github page。
答案 18 :(得分：1)
以下方法最适合我：
class MyClass {
public string prop1 { set; get; }
public object this[string propertyName]
{
get { return this.GetType().GetProperty(propertyName).GetValue(this, null); }
set { this.GetType().GetProperty(propertyName).SetValue(this, value, null); }
}
}
要获取属性值：
MyClass t1 = new MyClass();
...
string value = t1["prop1"].ToString();
设置属性值：
t1["prop1"] = value;
答案 19 :(得分：1)
看看Heleonix.Reflection库。您可以通过路径获取/设置/调用成员，或者创建比反射更快的getter / setter（lambda编译为委托）。例如：
var success = Reflector.Get(DateTime.Now, null, "Date.Year", out int value);
或一次创建一个吸气剂并缓存以备重用（这具有更高的性能，但如果中间成员为null，则可能会抛出NullReferenceException）：
var getter = Reflector.CreateGetter<DateTime, int>("Date.Year", typeof(DateTime));
getter(DateTime.Now);
或者，如果您要创建一个List<Action<object, object>>不同的getter，只需为编译的委托指定基本类型（类型转换将添加到编译的lambda中）：
var getter = Reflector.CreateGetter<object, object>("Date.Year", typeof(DateTime));
getter(DateTime.Now);
答案 20 :(得分：0)
这是我的解决方案。它也适用于COM对象，并允许从COM对象访问集合/数组项。
public static object GetPropValue(this object obj, string name)
{
foreach (string part in name.Split('.'))
{
if (obj == null) { return null; }
Type type = obj.GetType();
if (type.Name == "__ComObject")
{
if (part.Contains('['))
{
string partWithoundIndex = part;
int index = ParseIndexFromPropertyName(ref partWithoundIndex);
obj = Versioned.CallByName(obj, partWithoundIndex, CallType.Get, index);
}
else
{
obj = Versioned.CallByName(obj, part, CallType.Get);
}
}
else
{
PropertyInfo info = type.GetProperty(part);
if (info == null) { return null; }
obj = info.GetValue(obj, null);
}
}
return obj;
}
private static int ParseIndexFromPropertyName(ref string name)
{
int index = -1;
int s = name.IndexOf('[') + 1;
int e = name.IndexOf(']');
if (e < s)
{
throw new ArgumentException();
}
string tmp = name.Substring(s, e - s);
index = Convert.ToInt32(tmp);
name = name.Substring(0, s - 1);
return index;
}
答案 21 :(得分：0)
这是我根据其他答案得到的。在错误处理方面变得如此具体，有些矫over过正。
public static T GetPropertyValue<T>(object sourceInstance, string targetPropertyName, bool throwExceptionIfNotExists = false)
{
string errorMsg = null;
try
{
if (sourceInstance == null || string.IsNullOrWhiteSpace(targetPropertyName))
{
errorMsg = $"Source object is null or property name is null or whitespace. '{targetPropertyName}'";
Log.Warn(errorMsg);
if (throwExceptionIfNotExists)
throw new ArgumentException(errorMsg);
else
return default(T);
}
Type returnType = typeof(T);
Type sourceType = sourceInstance.GetType();
PropertyInfo propertyInfo = sourceType.GetProperty(targetPropertyName, returnType);
if (propertyInfo == null)
{
errorMsg = $"Property name '{targetPropertyName}' of type '{returnType}' not found for source object of type '{sourceType}'";
Log.Warn(errorMsg);
if (throwExceptionIfNotExists)
throw new ArgumentException(errorMsg);
else
return default(T);
}
return (T)propertyInfo.GetValue(sourceInstance, null);
}
catch(Exception ex)
{
errorMsg = $"Problem getting property name '{targetPropertyName}' from source instance.";
Log.Error(errorMsg, ex);
if (throwExceptionIfNotExists)
throw;
}
return default(T);
}